Ensure that enough registered segments are available and usable for query resource requests. If the number of unavailable or unregistered segments is higher than a set limit, then query resource requests are rejected. Also ensure that the variance of dispatched virtual segments across physical segments is not greater than the configured limit. See Rejection of Query Resource Requests.

Use multiple master and segment temporary directories on separate, large disks (2TB or greater) to load balance writes to temporary files (for example, /disk1/tmp /disk2/tmp). For a given query, HAWQ will use a separate temp directory (if available) for each virtual segment to store spill files. Multiple HAWQ sessions will also use separate temp directories where available to avoid disk contention. If you configure too few temp directories, or you place multiple temp directories on the same disk, you increase the risk of disk contention or running out of disk space when multiple virtual segments target the same disk.